My Ladybug has significant blade play - makes me hesitant to recommend. Although the size is suitable for a keychain.
For the same money, or less, the Ultimate Pen Knife from AG Russell is much better made. No lock though - you have to move up to the 2.5 Titanium (2" closed) to get a lock. The model Harkamus recommended is the 3.0 Titanium (3" closed), a bit larger.
If a lock isn't absolutely critical, I strongly recommend a small Swiss Army knife from Victorinox or Wenger. None of the small models have locks, but they have a variety of other tools that you may find useful on a daily basis - toothpick, tweezers, scissors, pen, bottle/can openers, etc. For particular models, check out the Stylus, Signature, Signature Lite, Classic SD, etc., etc., etc.